This invention relates to a laser machining device for surface treating an object or workpiece by a laser beam,
Laser machining devices are used in various fields. In a laser machining device in general, a laser beam is emitted along an optical or beam path and focussed on the object as a beam dot. In one of the fields, indents are formed into the object at such beam dots in a predetermined pattern. The object is typically a sheet of steel. The surface treatment is called dull processing in the art.
In order to generate the laser beam, a laser beam source is placed perliminarily in the laser machining device on actually surface treating object. The laser beam source may comprise a laser diode.
In the manner which will later be described with reference to one of several drawing figures of the accompanying drawing, a conventional laser machining device comprises a table or worktable which is movable relative to the optical path and is for carrying the object. A control unit is used to control movement of the table relative to the optical path and operation of a mechanical beam shutter or switch which is placed transversely of the optical path to carry out on-off control of the laser beam. The predetermined pattern is decided by relative movement between the table and the optical path and by timing of the on-off control of the laser beam. It is to be noted in connection with the conventional laser machining device that the laser beam can not be on-off controlled at a high on-off rate or speed.
In the meanwhile, an excellent Q switch is disclosed in U.S. Pat. No. 3,434,073 issued to John F. Forkner. The Q switch can be used in place of the mechanical beam shutter to on-off control the laser beam. It is, however, impossible to stably surface treat the object with the Q switch. This is because the laser beam source is subjected to different conditions of operation when the Q switch is used to on-off control the laser beam at different on-off rates. The Q switch is an example of acousto-optic modulators.